I don't know if it matters, but I see that your fuel pump uses a return line. Mine doesn't.

Here's my fuel pump...(actually Boofer's, but mine's the same). I have no return line (D)

It may matter.. I read where you'd posted in another thread about how your vent hose runs to the fuel inlet (like mine does) rather than to the stern. It seems mine runs to a point in the system that is behind the fuel cap, and that it has no access to atmosphere unless the cap is off or leaking.

Another poster seems to think his boat does the same thing unless he leaves his fuel cap a little loose, which is consistent with what my system would do..